GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Waterproofing Membrane for CMU

Adam Lazenby | Posted in Green Products and Materials on

Hey everyone,
I’ve excavated the foundation of our home in southern Ontario and had the compromised foundation fixed. Next step is a new weeping tile and waterproofing. My question is what type of waterproofing membrane will work best in this situation. The CMU below grade is most from the 1950s and is flat on the outside but above grade it has a textured surface. Also on the corners there are some half blocks in which there is a hollow facing the exterior. What do you all suggest for waterproofing? My gut says a peel and stick likely won’t adhere well to the textured block but this is a new realm for me. Any insight or product suggestion would be super helpful!  Remember I’m in Canada so hopefully we can find most products here.  I’ve attached a few photos so you can see the situation.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Bryan Coplin | | #1

    Hi Adam,

    A recent article was published on this topic you might find helpful:

    Others may have specific product recommendations.

  2. GBA Editor
    Kiley Jacques | | #2

    Hi Adam,

    I have heard one builder with a similar situation recommend Sika Waterproofing Systems. His house has weathered a major hurricane since he installed it, and he says there have been no leaks.

  3. Jamie B | | #3

    Hi Adam,

    You'll have a hard time finding sika products in non commercial settings. Tremco or Henry products are easier to get from construction distributors around here in Toronto and I'll assume wherever else you in Ontario. I've used CDS to get my waterproofing stuff in the past but you'll have to create a business account. ( otherwise homedepot has some consumer grade stuff.

    I suggest you fill the half blocks with mortar, mostly to give a surface for the membrane.

    Do a roll on liquid membrane as per the specs (since it's block I would use a mesh for ease of mind, but that's me). You don't need to waterproof the above grade bricks.

    Then do a drainage layer (dimple sheeting) remember to point the dimples towards the wall. This reduces the hydrostatic pressure against the membrane and let's water drip down to the weeping system. I believe this is key for longevity.

    Backfill with the dirt you have or gravel for better drainage.


Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |